Move screen off test from Proxy test class to regular host test class

ProxyMediaRouter2HostSideTest runs all tests with MEDIA_CONTENT_CONTROL,
which is now allowed to do screenOffScanning.

This is a cherrypick of 6907bb90f740a40398ebc9493d8837c897a13495.

Bug: b/352401364
Test: atest CtsMediaHostTestCases
Flag: TEST_ONLY
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:8fad1ceeca5482e4391aea3f8446d9aa26b42766)
Merged-In: I6f223fc37c563db1b62f61bb81428001f07dc443
Change-Id: I6f223fc37c563db1b62f61bb81428001f07dc443
4 files changed